2. The water cycle, also known as
the hydrological cycle or H2O cycle,
describes the continuous movement of
water on, above and below the surface of
the Earth. Although the balance of water on
Earth remains fairly constant over time,
individual water molecules can come and
go, in and out of the atmosphere.

4. There are some processes which take place
during the Water Cycle.
The processes are-
1. Evaporation
2. Condensation
3. Precipitation
4. Transpiration
5. Surface Runoff

5. The transformation of water from liquid
to gas phases as it moves from the ground
or bodies of water into the overlying
atmosphere.The source of energy for
evaporation is primarily Solar radiation.
Evaporation often implicitly
includes transpiration from plants, though
together they are specifically referred to
as evapotranspiration.Total annual
evapotranspiration amounts to
approximately 505,000
km3 (121,000 cu mi) of water, 434,000
km3 (104,000 cu mi) of which evaporates
from the oceans.

6. Water vapor in the air gets cold and changes
back into liquid, forming clouds.This is called
condensation.
You can see the same sort of thing at home...
pour a glass of cold water on a hot day and
watch what happens. Water forms on the
outside of the glass. That water didn't
somehow leak through the glass! It actually
came from the air. Water vapor in the warm
air, turns back into liquid when it touches the
cold glass.

7. Condensed water vapor that falls to
the Earth's surface . Most
precipitation occurs as rain, but also
includes snow, hail, fogdrip, graupel
and sleet. Approximately 505,000
km3(121,000 cu mi) of water falls as
precipitation each year, 398,000
km3 (95,000 cu mi) of it over the
oceans.

8. Transpiration is the process by
which moisture is carried through
plants from roots to small pores on
the underside of leaves, where it
changes to vapor and is released
to the atmosphere.Transpiration is
essentially evaporation of water
from plant leaves.Transpiration
also includes a process called
guttation, which is the loss of
water in liquid form from the
uninjured leaf or stem of the plant,
principally through water stomata.

9. When rain hits saturated or impervious ground it
begins to flow overland downhill. It is easy to see if
it flows down your driveway to the curb and into a
storm sewer, but it is harder to notice it flowing
overland in a natural setting. During a heavy rain
you might notice small rivulets of water flowing
downhill.Water will flow along channels as it moves
into larger creeks, streams, and rivers.This picture
gives a graphic example of how surface runoff (here
flowing off a road) enters a small creek.The runoff
in this case is flowing over bare soil and is
depositing sediment into the river (not good for
water quality).The runoff entering this creek is
beginning its journey back to the ocean.

10.  The water cycle provides natural filtration of
water and returns clean fresh water to the
earth.When water evaporates, all impurities
and contaminants are left behind and only
pure water vapor escapes.Without this
powerful filtration system, we would soon
contaminate all the water on earth and
would run out of fresh water.

11. The water cycle is powered from solar energy.
86% of the global evaporation occurs from
the oceans, reducing their temperature by
evaporative cooling.Without the cooling, the
effect of evaporation on the greenhouse
effect would lead to a much higher surface
temperature of 67 °C (153 °F), and a warmer
planet.